Technical Pens, Polystyrene & You

I have a question for one of the countless modeling experts (scale, not 
fashion!) on the list:

Technical / engineering pens are mentioned in the Painting FAQ as an
easy 
way to do black-lining.  Are they equally effective on both primed minis
AND 
regular model plastic (I'm guessing it's made out of polystyrene)?

I recently picked up a couple of snap-together 1/144 scale Gundam Wing 
mecha, and while I'm too lazy to paint them, I'm convinced that black- 
lining around the armor panels would add a lot, and tech pens seem the 
easiest method.

I'm looking for recommendations.  What brand should I get if I'm looking
for 
an inexpensive, widely-available (in the US) technical pen that won't
smudge 
on (unprimed, unpainted) model plastic?

Incidentally, these kits are pretty nice.  About US$12 for a 5"-tall
giant 
robot.	They seem about right for Stargrunt, but I'm more interested in 
utilizing them in Full Thrust for Super Dimensional Fortress Macross
style 
scenarios.

Thanks for any assistance.

-SRB
(formerly trapper@nwlink.com)

--
"Meditate upon exile, torture, wars, diseases, shipwreck, so that you
may 
not be a novice to any misfortune." -Seneca

________________________________________________________________________
_
Get Your Private, Free E-mail from MSN Hotmail at
http://www.hotmail.com.

Share information about yourself, create your own public profile at 
http://profiles.msn.com.